Airplane with unswept slotted cruise wing airfoil

ABSTRACT

Slotted cruise airfoil technology allows production of a substantially unswept wing that achieves the same cruise speed as today&#39;s conventional jet airplanes with higher sweep. This technology allows the wing boundary layer to negotiate a strong recovery gradient closer to the wing trailing edge. The result is about a cruise speed of Mach=0.78, but with a straight wing. It also means that for the same lift, the super velocities over the top of the wing can be lower. With very low sweep and this type of cruise pressure distribution, natural laminar flow will be obtained. In addition, heat is transferred from the leading edge of the wing and of the main flap to increase the extent of the natural laminar flow. The slotted cruise wing airfoil allows modularization of the wing and the body for a family of airplanes. The unsweeping of the wing significantly changes the manufacturing processes, reduces manufacturing costs and flow time from detail part fabrication to airplane delivery. The system architecture is all new for cost reduction. A high wing arrangement allows more freedom for installation of higher bypass ratio advanced geared fan engines. A low is wing in conjunction with aft body mounted engines will have a similar effect. Aerodynamic efficiency and engine fuel burn efficiency result in considerable lower emission of noise and greenhouse gases.

This application claims the benefit of U.S. Provisional Application No.60/028,853, filed Oct. 22, 1996.

FIELD OF THE INVENTION

This invention relates to an aircraft configuration and, moreparticularly, to a commercial jet aircraft utilizing a slotted cruiseairfoil and a wing with very low sweep compared to the sweep of moreconventional jet aircraft, achieving the same cruise speed.

BACKGROUND OF THE INVENTION

This invention relates to an aircraft configuration utilizing improvedlaminar flow. If laminar flow is achieved, aircraft drag, manufacturingaims, and operating costs are substantially reduced. U.S. Pat. No.4,575,030, entitled, “Laminar Flow Control Airfoil” by L. B. Gratzer,and is assigned to the assignee of this invention. The Gratzer patentprovides information on development which includes, among othertechniques, suction surfaces and slots to promote natural laminar flowover a main box region of a wing.

SUMMARY OF THE INVENTION

An aspect of the wing of this invention is that it incorporates aslotted cruise airfoil. Slotted cruise airfoil technology that we havedeveloped allows us to produce an unswept, or substantially unswept,wing that achieves the same cruise speed as today's conventionalairplanes with higher sweep.

This invention, this technology allows the wing boundary layer tonegotiate a strong recovery gradient closer to the wing trailing edge.The result is about a cruise speed of Mach=0.78, but with a straightwing. It also means that for the same lift, the super velocities overthe top of the wing can be lower. With very low sweep and this type ofcruise pressure distribution, natural laminar flow can easily beobtained. Lower-surface Krueger flaps are installed to increase liftcapability for low-speed operation and to protect the wing leading edgefrom bugs during takeoff and landing to prevent spoiling natural laminarflow.

In another aspect of the invention, heat is transferred from the leadingedges of the wing and/or of the main flap to increase the extent of thenatural laminar flow.

In still another aspect of this invention, a high wing arrangementallows more freedom for installation of higher bypass ratio engines. Anadvanced geared fan engine, by-pass ratio 12 or higher, is a possibilitythat could be easily installed under the high wing. The lower supervelocities of the slotted cruise airfoil make the body shock problemassociated with many high wing airplanes less of a concern here.

The slotted cruise wing airfoil and the straight wing allow us tomodularize the wing and the body so that we can develop a family ofairplanes by intermixing different bodies with different wings.

Another aspect of this invention is to reduce costs. The unsweeping ofthe wing significantly changes the manufacturing processes, reducesmanufacturing costs and flow time from detail part fabrication toairplane delivery. The system architecture is all new rather than amajor remodeling of a systems architecture from an exiting airplane. Itis a top down approach geared towards the requirements of this airplane.Components from existing products will be used whenever they satisfy therequirements of this airplane. The payload systems allow for flexibleinteriors and extensive use of molded panels.

Still another aspect of this invention is that the expected fuel bum perseat for this type of an airplane is 20% to 30% less than on current jetairplanes, this can be associated with considerable reduction ofemission of greenhouse gases.

There is very little difference in ditching capability between a lowwing airplane and a high wing airplane. In both cases, the body providesthe vast majority of the flotation. The wing provides some stability toprevent the ditched airplane from rolling over.

Another aspect of this invention is that a low wing version with aftmounted engines is also possible. It would feature many, if not most ofthe above advantages.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1a through 1c compare the straight wing arrangements with theconventional wing.

FIGS. 2a through 2c compare the effect of the straight wing on theconfigurations with the conventional wing.

FIG. 3 is an isometric view of the high wing version of FIGS. 1 and 2with a ‘T’-tail.

FIG. 4 is an isometric view of the high wing version of FIGS. 1 and 2with an alternative ‘V’-tail empennage arrangement.

FIG. 5 is an isometric view of the low wing version of FIGS. 1 and 2.

FIGS. 6a and 6b illustrate the details of the slotted airfoil.

FIGS. 7a and 7b compare the pressure distributions for a conventionalairfoil and slotted airfoil (7a is conventional).

FIG. 8 shows a drag rise comparison between a conventional airfoil and aslotted airfoil.

FIG. 9, the pie-chart illustrates the recurring cost distribution for aconventional wing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The illustrations on FIGS. 1 and 2 serve for the explanation between anexisting, prior art airplane configuration as a reference, and twodifferent new arrangements that are the subject of this patentapplication.

On the prior art reference airplane, FIGS. 1a and 2a, a swept wing 1 isattached to the bottom of the fuselage 5. The basic components of thewing 1 consist of a structural box, which is divided into a left-handexposed part 2, a center section 3, and a right-hand exposed part 4.Medium bypass ratio engines 6 are attached to struts 7 below the wing.The main landing gear 8 is suspended from the wing 1. Its support bymeans of a trunnion requires space within a wing trailing edge extension9, also called a ‘Yehudi’. Wing leading edge devices 10 are of thecommon type, slats or Krueger flaps or a combination thereof. Trailingedge devices are flaps 11, spoilers 12 and ailerons 13. The length ofthe main landing gear 8 is determined by engine 6 ground clearance androtation angle of the airplane. The aft fuselage 5 also shows an‘upsweep’ angle 36 for airplane rotation during take-off and landing.

On the ‘high wing’ example of the invention, FIG. 1b and 2b, an unsweptwing 14 is attached to the top of the fuselage 15. Its structural box 16is a single part, reaching from wing tip to wing tip. It is formed bythe rear spar 39, front spar 82, upper 83 and lower 84 wing skins.Additional spars in intermediate positions between the rear spar 39 andthe front spar 82 could also be included. High bypass ratio engines 17are attached to struts 18 below the while. The main landing gear 19 isattached to the fuselage 15, not requiring additional space in the wingplatform 14. Wing leading edge devices 20 are Krueger flaps. Spoilers 21are of the same type as on the reference airplane. However, the flaps 23represent the ‘vane-main’ feature with the addition of a slot that ispermanent for all flap positions and is a unique key to this invention.More detail is shown on FIG. 6. The slots are extended outboardthroughout the ailerons 22. Heat is transferred from the leading edge ofthe wing 14 and/or of the main flap 23 to increase the extent of naturallaminar flow. The Main landing gear 19 is shorter than the gear on thereference airplane. The aft fuselage 15 is more symmetric, ends in avertical blade shape, and features less upsweep angle 37 and less dragthan on the reference airplane due to the features of the ‘slotted wing’14. Compared to a low wing, the high wing 14 allows for a betterdistribution of the cast Aluminum passenger doors 24, with unobstructedescape slides. The lower deck cargo compartment 25 capacity is alsoincreased because of the absence of the wing box.

On the ‘low wing’ example of the invention, FIGS, 1c and 2c, an unsweptwing 26 is attached to the bottom of the fuselage 27. Its structural box28 is a single part, reaching from tip to tip. High bypass ratio engines29 are attached to struts 30 at both sides of the aft fuselage 27. Themain landing gear 31 is attached to the fuselage 27, of requiringadditional space in the wing platform 26. Wing leading edge devices 20,spoilers 21 and ailerons 22 are of the same type and shape as on theprevious airplane. The flaps 23 represent the ‘vane-main’ feature withthe addition of a slot that is permanent for all flap positions and is aunique key to this invention. More detail is shown on FIG. 6. These areof the same type and shape as on the previous airplane. The slots arealso extended outboard throughout the ailerons. Heat is transferred fromthe leading edge of the wing 26 and/or of the main flap 23 to increasethe extent of natural laminar flow. The main landing gear 31 is shorterthan the gear on the reference airplane. The aft fuselage 27 is moresymmetric, ends in a vertical blade shape, and features less upsweepangle 38 and less drag than on the reference airplane due to thefeatures of the ‘slotted wing’ 26. Basically, the shape and size of thewing 26 and the fuselage 27 are similar to the airplane in FIGS. 1b and2b.

The embodiments of the whole airplane configurations are shown on FIGS.3 through 5. All three figures represent examples of this invention.

FIG. 3 is an isometric view of the high wing version, FIGS. 1b and 2b.The empennage arrangement resembles a ‘T’-tail 32. The nose landing gear33 is shorter than on the Reference airplane, because of the closeground proximity.

FIG. 4 is another isometric view of the high wing 14 version, FIGS. 1band 2b with an alternative empennage arrangement. The ‘T’-tailarrangement of FIG. 3 has been replaced by a ‘V’-shape 34.

FIG. 5 is an isometric view of the low wing 26 version, FIGS. 1c and 2c.The nose landing gear 35 is shorter than on the reference airplane,because of the close ground proximity.

FIG. 6 is extracted from the concurrent patent application Ser. No.08/735,233, filed Oct. 22, 1996 entitled, “Slotted Cruise Trailing EdgeFlap” by G. L. Siers. The two views, FIGS. 6a and 6b illustrate the twoextreme positions of the trailing edge flap.

Of particular interest is the wing rear spar 39 shown in combinationwith the rear fragment of a wing 14 or 26. The components of the flap 23are generally located aft of, and are structurally supported by, thewing rear spar 39.

In general, a slotted cruise trailing edge flap 23 formed in accordancewith the application Ser. No. 08/735,233 has a single-slottedconfiguration during cruise, FIG. 6a and a double-slotted configurationduring takeoff(not shown) and landing, FIG. 6b. This is accomplished bya flap assembly 23 that is movable between a stowed position and anextended position. In the stowed position a single slot is present, andin the extended position two slots are present. More specifically, flapassembly 23 includes two airfoil elements, a vane element and a mainelement, that are arranged in fixed relation to one another. The spacebetween the airfoil elements forms a permanent single slot. At varioussupport locations along the wing trailing edge, the flap assembly 23 ismovably connected to an extension assembly 40 that is secured to thewing rear spar 39.

The extension assembly 40 includes a support structure to which the flapassembly 23 is translatable and rotatably connected. The extensionassembly 40 further includes an actuation mechanism that moves the flapassembly 23 relative to the support structure. In a stowed position, thevane element of flap 23 nests into the wing 14 or 26 such that thepermanent single slot remains available to direct airflow from regionsbelow the wing to regions above the wing. In an extended position, thevane and main elements of flap 23 form a double-slotted arrangement byrotating downward and translating rearward relative to the wing 14 or26.

Physical factors limiting the performance of transonic cruise airfoils

In the following discussion, “airfoil” refers to the cross-sectionalshape of a wing in planes that are substantially longitudinal andvertical, which plays a major role in determining the aerodynamicperformance of said wing. “Transonic cruise” refers to operation of thewing at high subsonic speed such that the airflow past the wing containslocal regions of supersonic flow. “Mach number” refers to the ratio ofthe flow speed to the speed of sound.

The performance of an airfoil in transonic cruise applications can becharacterized by four basic measures:

-   -   1) The airfoil thickness, usually expressed as the        maximum-thickness ratio (maximum thickness divided by chord        length). Thickness is beneficial because it provides the room        needed for fuel and mechanical systems and because a wing        structure with greater depth can be lighter for the same        strength.    -   2) The speed or Mach number at the preferred operating condition        The Mach number capability of the airfoil, modified by a factor        related to the sweep angle of the wing, contributes directly to        the cruise speed of the airplane.    -   3) The lift coefficient at the preferred operating condition.        Increased lift coefficient is advantageous because it could        allow increased weight (e.g. more fuel for longer range) or a        higher cruise altitude.    -   4) The drag coefficient at the preferred operating condition and        at other operating conditions that would be encountered in the        mission of an airplane. Reducing the drag reduces fuel        consumption and increases range.

Other measures such as the pitching-moment characteristics and the liftcapability at low Mach numbers are also significant, but are lessimportant than the basic four.

Together, the four basic performance measures define a level ofperformance that is often referred to as the “technology level” of anairfoil. The four basic performance measures impose conflictingrequirements on the designer in the sense that design changes intendedto improve one of the measures tend to penalize at least one of theother three. A good design therefore requires finding a favorablecompromise between the four measures.

At any given technology level, it is generally possible to design a widerange of individual airfoils tailored to different preferred operatingconditions and representing different trade-offs between the four basicperformance measures. For example, one airfoil could have a higheroperating Mach number than another, but at the expense of lower lift andhigher drag. Given modern computational fluid dynamics tools, designingdifferent airfoils at a given technology level is generally astraightforward task for a competent designer. On the other hand,improving the technology level, say by improving one of the basicperformance measures without penalizing any of the other three, tends tobe more difficult, and the more advanced the technology level one startswith, the more difficult the task becomes. Starting with an airfoil thatis at a technology level representative of the current state of the art,it can be extremely difficult to find significant improvements.

The main factors that limit performance are associated with the physicsof the flow over the upper surface of the airfoil. To understand thesefactors, it helps to look at a typical transonic cruise airfoil pressuredistribution, plotted in terms of the pressure coefficient C_(P) on anegative scale, as shown in FIG. 7(a). For reference, the shape of theairfoil is shown just below the pressure-distribution plot. On the C_(P)scale shown, C_(P)=0 is the static pressure of the freestream flow farfrom the airfoil, which is assumed to be at a subsonic speed. At eachpoint on the surface, the value of C_(P), in addition to defining thepressure, corresponds to a particular value of the floss velocity justoutside the thin viscous boundary layer on the surface. Negative C_(P)(above the horizontal axis) represents lower pressure and highervelocity than the freestream. while positive C_(P) (below the horizontalaxis) corresponds to higher pressure and lower velocity. A particularlevel of negative C_(P) corresponds to sonic velocity and is shown bythe dotted line 41.

The lower curve 42 on the pressure-distribution plot represents thepressure on the lower surface 43, or high-pressure side, and the uppercurve 44 represents pressure on the upper-surface 45. The verticaldistance between the two curves indicates the pressure differencebetween the upper and lower surfaces, and the area between the twocurves is proportional to the total lift generated by the airfoil. Notethat near the leading edge there is a highly positive spike in the C_(P)distribution 46 at what is called the “stagnation point” 47, where theoncoming flow first “attaches” to the airfoil surface, and the flowvelocity outside the boundary layer is zero. Also, note that the upper-and lower-surface C_(P) distributions come together at the trailing edge48, defining a single value of C_(P) 49 that is almost always slightlypositive. This level of C_(P) at the trailing edge, as will be seenlater, has an important impact on the flow physics. Because thetrailing-edge C_(P) is dictated primarily by the overall airfoilthickness distribution, and the thickness is generally constrained by anumber of structural and aerodynamic factors, trailing-edge C_(P) issomething over which the designer has relatively little control. Awayfrom the leading-edge stagnation point and the trailing edge, thedesigner, by varying the airfoil shape, has much more control over thepressure distribution.

For a given airfoil thickness and Mach number, the problem of achievinga high technology level boils down to the problem of maximizing the liftconsistent with a low drag level. Increasing the lift solely byincreasing the lower-surface pressure is generally not possible withoutreducing airfoil thickness. Thus the designer's task is to reduce theupper-surface pressure so as to produce as much lift as possible, but todo so without causing a large increase in drag. In this regard, thepressure distribution shown in FIG. (7a) is typical of advanced designpractice. The operating condition shown is close to the preferredoperating condition that might be used for the early cruise portion ofan airplane mission. The drag at this condition is reasonably low, butat higher Mach numbers and/or lift coefficients, the drag would increaserapidly.

Note that the upper-surface C_(P) 44 over the front half of the airfoilis above the dotted line 41, indicating that the flow there is mildlysupersonic. Just aft of midchord, this supersonic zone is terminated bya weak shock, indicated on the surface as a sudden increase in C_(P) 50to a value characteristic of subsonic flow. The C_(P) distribution inthe supersonic zone 51 is deliberately made almost flat, with only anextremely gradual pressure rise, in order to keep the shock frombecoming stronger and causing increased drag at other operatingconditions. The shock is followed by a gradual pressure increase 52,referred to as a “pressure recovery”, to a slightly-positive C_(P) 49 atthe trailing edge. The location of the shock and the pressuredistribution in the recovery region are carefully tailored to strike abalance between increased lift and increased drag.

Trying to increase the lift will tend to move the airfoil away from thisfavorable balance and increase the drag. For example, one way of addinglift would be to move the shock 50 aft. This, however, would require asteeper recovery (because the immediate post-shock C_(P) and thetrailing-edge C_(P) are both essentially fixed), which would cause theviscous boundary layer to grow thicker or even to separate from thesurface, either of which would result in a significant drag increase.The other obvious way to increase lift would be to lower the pressureahead of the shock even further (move the C_(P) curve 51 upward over theforward part of the airfoil and increase the supersonic flow velocitythere), but this would increase the pressure jump across the shock,which would result in an increase in the so-called shock drag. Forsingle-element transonic airfoils at the current state of the art, thiscompromise between lift and drag has reached a high level of refinement,and it is unlikely that any large improvement in technology levelremains to be made.

Potential technology advantage of the slotted airfoil

The shape and resulting pressure distribution of a slotted transoniccruise airfoil are shown in FIGS. (6) and (7b). The airfoil 23 consistsof two elements (a forward element 60 and an aft element 61) separatedby a curved channel (62, the slot) through which air generally flowsfrom the lower surface 84 to the upper surface 64. In this example, theslot lip (65, the trailing edge of the forward element) is just aft of80 percent of the overall chord from the leading edge, and the overlapof the elements is about 3 percent of the overall chord. Pressuredistributions are shown for both elements, so that the pressuredistributions overlap where the airfoil elements overlap. As with theconventional airfoil, the upper curves 66,67 give the C_(P)distributions on the upper surfaces 64,83, and the lower curves 68,69give C_(P) on the lower surfaces 84,70. Note that there are twostagnation points 71,72 and their corresponding high-pressure spikes73,74, one on each element, where the oncoming flow attaches to thesurface near each of the leading edges.

To begin the consideration of the flow physics, note that the preferredoperating condition for the slotted airfoil shown is faster than that ofthe single-element airfoil (Mach 0.78 compared with 0.75), and that thelift coefficient is slightly higher, while both airfoils have the sameeffective thickness for structural purposes. At the slotted airfoil'soperating condition, any single-element airfoil of the same thicknesswould have extremely high drag. The slotted airfoil's substantialadvantage in technology level results from the fact that the finalpressure recovery 75 is extremely far aft, beginning with a weak shock76 at about 90 percent of the overall chord. Such a pressuredistribution would be impossible on a single-element airfoil becauseboundary-layer separation would surely occur, preventing the shock frommoving that far aft. The mechanism, loosely termed the “slot effect”, bywhich the slot prevents boundary-layer separation, combines severalcontributing factors:

-   -   1) The boundary layer on the upper surface 83 of the forward        element is subjected to a weak shock 77 at the slot lip 65, but        there is no post-shock pressure recovery on the forward element.        This is possible because the aft element 61 induces an elevated        “dumping velocity” at the trailing edge of the forward element        (The trailing-edge C_(P) 78 on the forward element is strongly        negative, where on a single-element airfoil the trailing-edge        C_(P) is generally positive).    -   2) The upper- and lower-surface boundary layers on the forward        element combine at the trailing edge 65 to form a wake that        flows above the upper surface 64 of the aft element and that        remains effectively distinct from the boundary layer that forms        on the upper surface of the aft element. Over the of part of the        aft element, this wake is subjected to a strong pressure rise        75,76, but vigorous turbulent mixing makes the wake very        resistant to flow reversal.    -   3) The boundary layer on the upper surface 64 of the aft element        has only a short distance over which to grow, starting at the        stagnation point 72 near the leading edge of the aft element, so        it is very thin when it encounters the final weak shock 76 and        pressure recovery 75, and is able to remain attached. With        regard to its pressure distribution and boundary-layer        development, the aft element is, in effect, a separate airfoil        in its own right, with a weak shock and pressure recovery        beginning at about the mid-point of its own chord, for which we        would expect attached flow to be possible.

The upper-surface pressure distribution of FIG. 7(b) is a relativelyextreme example of what the slot effect makes possible. A range ofless-extreme pressure distributions intermediate between that shown inFIG. 7(b) and the single-element pressure distribution of FIG. 7(a) canalso take advantage of the slot effect. The shock on the forward elementdoes not have to be all the way back at the slot lip, and there does nothave to be a supersonic zone on the upper surface of the aft element. Infact, the airfoil of FIG. 7(b) displays a sequence of such intermediatepressure distributions when operating at lower Mach numbers and liftcoefficients than the condition shown. The slot effect is still neededto prevent flow separation at these other conditions.

One way of comparing the technology levels of airfoils is to plot thedrag-rise curves (drag coefficient versus Mach number at constant liftcoefficient), as shown in FIG. (8). Here the dashed curve 80 is for thesingle-element airfoil of FIG. 7(a) at a lift coefficient Cl of 0.75,and the solid curve 81 is for the slotted airfoil of FIG. 7(b) at aslightly higher Cl of 0.76. It is clear that the low-drag operatingrange of the slotted airfoil extends up to 0.03 Mach faster than thesingle-element airfoil, with slightly higher lift and the samethickness. Of course the slotted airfoil could be redesigned to use thistechnology advantage for purposes other than higher speed, for example,to achieve even higher lift at the same speed as the single-elementairfoil.

The pressure distribution on the lower surface also contributes to thetechnology level of the slotted airfoil of FIG. 7(b). Compare thepressure distribution 68 on the lower surface 84 of the forward elementof the slotted airfoil with the corresponding pressure distribution 42on the lower surface 43 of the single-element airfoil of FIG. 7(a). Theflatter pressure distribution on the slotted airfoil results in lesscurvature of the lower surface of the airfoil and greater depth of theairfoil at the locations where the front and rear spars of the mainstructural box would be placed (typically about 15 percent and 64percent of the overall chord). Flatter lower-surface skins and deeperspars are both favorable to the structural effectiveness of the main boxstructure. In the design of the airfoil of FIG. 7(b) this advantage wastraded so as to contribute to the improved Mach number and liftcoefficient, while keeping the structural effectiveness (bendingstrength) of the wing box the same as that of the single-element airfoilof FIG. 7(a).

The unsweeping of the wing significantly changes the manufacturingprocesses, reduces manufacturing costs and flow time from detail partfabrication to airplane delivery. Conventional commercial jet airplanewings are built with structural splices where the stringers and sparschange direction, generally at the side of body. With an unswept wing,one of the spars has no changes in direction and no splice. Wing boxstructural stringers (skin panel stiffeners) are parallel to thestraight spar and do not have splices. As with the spar and stringers,the wing structural skin does not require spanwise splicing althoughchord wise splicing will be used when the limits of raw material makesingle piece wing skins impractical. Building the wing as a single piecerather than a left wing a right wing and a wing stub eliminates theparts associated with splicing and the labor and flow time required tojoin the left and right wing to the wing stub. Significant reductions inthe quantity of parts and manufacturing labor are a result of unsweepingthe wing. FIG. 9 represents conventional wing recurring costs, theoutboard wing cost represented by 91 will be reduced by 30%. Thissavings is the combination of eliminating the wing joints, and thereduction of wing shear and dihedral. Another 12% cost reduction couldbe realized with low cost graphite construction. The wing stub costrepresented by 92 will be reduced by 90% because it is not required.

Unsweeping the wing 14 changes the wing relationship with the mainlanding gear 19. Conventional swept wing commercial jet airplanesintegrate the landing gear into the portion of the wing aft of the rearspar 9. With the unswept high wing commercial jetliner configurationshown in FIGS. 1 through 5, the landing gear 19 is not integrated intothe wing at all, reducing the plan area of the wing and simplifying thewing aft of the rear spar 9. The cost reduction is relative to FIG. 9,the recurring cost of the fixed trailing edge (the non-moving parts ofthe wing aft of the rear spar) represented by 93 is reduced by 25%. Onedisadvantage of reducing the area of the fixed trailing edge is thereduction in wing thickness at the rear spar 39. This may result in arequirement for a mid spar or spars with more depth. The spoilers 21,fixed leading edge, moveable leading edge 20 and moveable trailing edge23 costs represented by 94 are not expected to change. The additionalcost associated with designing the slot 62 into the airfoil is expectedto be offset by the elimination of an inboard aileron and thesimplification of the high lift system.

Structural design advantages of the unswept wing include higher loadingof the front spar 82 and thereby unloading the rear spar 39 and aft partof the wing skins 83 and 84. This load redistribution results in theability to increase the structural aspect ratio of the wing whilemaintaining the same stress levels. Utilizing a mid spar or spars mayincrease the wing aspect ratio further with out increasing stresslevels.

The slotted cruise wing airfoil and the straight wing allow us tomodularize the wing 14 and the body 15, so that we can develop a familyof airplanes by intermixing different bodies with different wings.

Aspect Ratio is the ratio of (span)² divided by wing area. StructuralAspect Ratio is the ratio of (structural span)² divided by structuralwing area.

While preferred embodiments of the invention have been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A commercial jetplane capable of flying at acruise speed of Mach=0.78 or above, comprising: a fuselage; a landinggear mounted on said fuselage; a single wing attached to said fuselage,said single wing being substantially unswept with a high aspect ratio,and including: a forward airfoil element having an upper surface and alower surface; an aft airfoil element having an upper surface and alower surface; an internal structure comprising at least two sparsextending from one tip to an opposing tip of said single wing, with arear one of the spars being straight and unswept in plan view; anairfoil structure having a slot that allows airflow from the forwardairfoil element to the aft airfoil element, wherein during cruisingflight of the airplane, said airfoil structure having said slot divertssome of the air flowing along the lower surface of the forward airfoilelement to flow over the upper surface of the aft airfoil element, andwhere the lower surface of the forward airfoil element and the lowersurface of the aft airfoil element are shaped to provide an efficientcross section for a main structural box of the single wing; and saidwing and said fuselage being constructed of at least one of aluminum andgraphite composite.
 2. The airplane of claim 1 wherein said airfoilstructure having a slot produces natural laminar flow over the aftairfoil element of said single wing.
 3. The airplane of claim 1 whereinsaid airfoil structure having said slot produces natural laminar flowover the forward airfoil element of said single wing.
 4. The airplane ofclaim 1 wherein heat is transferred from a leading edge of at least oneof said wing and main flap to increase the extent of said naturallaminar flow.
 5. An airplane of claim 1 which comprises a “T”-tail typeempennage.
 6. The airplane of claim 1 which comprises a “V”-tail typeempennage.
 7. The airplane of claim 1 which comprises a low tail typeempennage.
 8. The airplane of claim 7, wherein at least two high bypassratio engines are attached to the airframe.
 9. The airplane of claim 8wherein said high bypass engines are geared fan engines or unducted fanswhich are energy efficient with reduced fuel consumption, noise andgreenhouse gas emissions.
 10. The airplane of claim 1 wherein thereduced rotation angle also decreases the aft body upsweep and reducesdrag.
 11. An airplane of claim 1 wherein said single wing is attached tothe top of said fuselage and the engines are attached below the wing.12. An airplane of claim 1 wherein said single wing is attached to thebottom of said fuselage and said engines are attached to the aft end ofthe fuselage.
 13. An aircraft, comprising: a fuselage; at least one wingattached to the fuselage, the wing having an upper surface, a lowersurface, and an internal structure including at least one spar; atrailing edge device carried by the wing, the trailing edge devicehaving an upper surface and a lower surface, the upper surface of thetrailing edge device being recessed away from an aft-extended contour ofthe wing upper surface in a thickness direction along its entire lengthwhen in a neutral, undeflected, undeployed position, at least one of theat least one wing and the trailing edge device having a spanwise slotthat allows airflow from the at least one wing to the trailing edgedevice, the slot having an aft-facing exit opening at an offset betweenthe upper surfaces of the at least one wing and the trailing edgedevice, the offset being in the thickness direction, wherein duringcruising flight of the aircraft, the slot diverts some of the airflowing along the lower surface of the at least one wing through theslot to flow over the upper surface of the trailing edge device, thelower surface of the at least one wing and the lower surface of thetrailing edge device being shaped to provide an efficient cross sectionfor a main structural box of the at least one wing; and landing geardepending from the fuselage.
 14. The aircraft of claim 13 wherein the atleast one wing is at least approximately unswept.
 15. The aircraft ofclaim 13 wherein the slot is configured to remain open at all flightconditions.
 16. The aircraft of claim 13 wherein the at least one wingis configured to operate at a cruise Mach number of 0.78 or higher. 17.The aircraft of claim 13 wherein the at least one spar includes aforward spar and an aft spar forming portions of opposing sides of awing box.
 18. The aircraft of claim 13 wherein the at least one wingincludes a forward spar and an aft spar and wherein at least one of theforward and aft spars is at least approximately unswept.
 19. Theaircraft of claim 13 wherein the at least one spar extends in an atleast generally straight line from one side of the fuselage to theother.
 20. The aircraft of claim 13 wherein the at least one wingincludes a single wing having a common structure extending from a firstside of the fuselage to a second side of the fuselage.
 21. The aircraftof claim 13 wherein the at least one wing includes a single wing havinga unitary structure extending from a first side of the fuselage to asecond side of the fuselage.
 22. The aircraft of claim 13 wherein the atleast one wing includes a structure extending from a first side of thefuselage to a second side of the fuselage without a splice.
 23. Theaircraft of claim 13 wherein the slot extends over less than an entirespan of the at least one wing.
 24. The aircraft of claim 13 wherein thewing includes an aileron, and wherein the slot extends spanwise througha region of the at least one wing containing the aileron.
 25. Theaircraft of claim 13 wherein the at least one wing includes a singlewing extending from a first tip on a first side of the fuselage to asecond tip on a second side of the fuselage, and wherein the at leastone wing further includes forward and aft spars, the forward sparextending from a first position at least proximate to the first tip to asecond position at least proximate to the second tip, the aft sparextending from a third position at least proximate to the first tip to afourth position at least proximate to the second tip.
 26. The aircraftof claim 13 wherein the slot is a first slot, and wherein the trailingedge device is movable relative to the at least one wing to form asecond slot forward of the first slot and divert additional air from thelower surface of the wing to the upper surface of the trailing edgedevice.
 27. The aircraft of claim 13 wherein at least one of the uppersurface and lower surface of at least one of the wing and the trailingedge device includes a composite material.
 28. The aircraft of claim 13,further comprising a propulsion system depending from at least one ofthe at least one wing and the fuselage.
 29. The aircraft of claim 13,further comprising an empennage aft of the at least one wing.
 30. Theaircraft of claim 13 wherein the slot is configured to divert airsufficient to increase a critical Mach number of the aircraft.
 31. Theaircraft of claim 13 wherein the slot is configured to divert airsufficient to increase a maximum cruise speed of the aircraft.
 32. Anaircraft, comprising: a fuselage, at least one wing attached to thefuselage, the at least one wing including: a forward airfoil elementhaving an upper surface and a lower surface; at least one sparpositioned within the forward airfoil element and extending in an atleast generally straight line from one side of the fuselage to theother; an aft airfoil element having an upper surface and a lowersurface, the aft airfoil element being coupled to the forward airfoilelement, the aft airfoil element having a leading edge spaced apart froma portion of the forward airfoil element with a slot positioned betweenthe portion of the forward airfoil element and the leading edge of theaft airfoil element, the slot being configured to be open during cruiseflight to divert some of the air flowing along the lower surface of theforward airfoil element to flow over the upper surface of the aftairfoil element; a propulsion system depending from at least one of theat least one wing and the fuselage; and landing gear depending from thefuselage.
 33. The aircraft of claim 32 wherein the at least one wing isconfigured for a subsonic cruise speed of at least Mach 0.78.
 34. Theaircraft of claim 32 wherein the at least one wing has an at leastapproximately unswept leading edge.
 35. The aircraft of claim 32 whereinthe at least one spar is at least approximately unswept.
 36. Theaircraft of claim 32 wherein the slot is configured to divert airsufficient to increase a critical Mach number of the aircraft.
 37. Theaircraft of claim 32 wherein the slot is configured to divert airsufficient to increase a maximum cruise speed of the aircraft.
 38. Theaircraft of claim 32 wherein the at least one wing includes a singlewing having a unitary structure extending from a first side of thefuselage to a second side of the fuselage.
 39. The aircraft of claim 32wherein the slot extends over less than an entire span of the at leastone wing.
 40. The aircraft of claim 32 wherein the at least one wing,includes an aileron, and wherein the slot extends spanwise through aregion of the at least one wing containing the aileron.
 41. An aircraftsystem, comprising: at least one wing having an upper surface shaped toinclude at least one transonic region during cruise flight; and a flapassembly that includes a forward airfoil element having an upper surfaceportion and a lower surface portion, and an aft airfoil element coupledto the forward airfoil element, the aft airfoil element having an uppersurface portion and a lower surface portion, at least a part of the aftairfoil element being spaced apart from a part of the forward airfoilelement by a fixed first slot, the first slot being configured to beopen during cruise flight to divert some of the air flowing along thelower surface portion of the wing to flow over the upper surface portionof the aft airfoil element, the first slot having an aft-facing exitopening at an offset between the upper surface of the wing and the uppersurface portion of the aft airfoil element, the offset being in thethickness direction, and wherein the forward airfoil element and the aftairfoil element are movable as a unit relative to the at least one wingto open a second slot between the forward airfoil element and the atleast one wing, the forward and aft airfoil elements having a fixedangular relationship with each other when the second slot is open andwhen the second slot is closed.
 42. The aircraft system of claim 41wherein the at least one wing is shaped to be efficient at a transoniccondition.
 43. The aircraft system of claim 41, further comprising: afuselage coupled to the at least one wing, a propulsion system dependingfrom at least one of the at least one wing and the fuselage; and landinggear depending from at least one of the at least one wing and thefuselage.
 44. The aircraft system of claim 41 wherein the at least onewing is at least approximately unswept.
 45. The aircraft system of claim41 wherein the at least one wing overlaps the trailing edge assembly bythree percent of a combined chord length of the at least one wing andthe flap assembly when the flap assembly is stowed.
 46. The aircraftsystem of claim 41 wherein the slot extends over less than an entirespan of the at least one wing.
 47. The aircraft system of claim 41wherein the at least one wing includes an aileron, and wherein the slotextends spanwise through a region of the at least one wing containingthe aileron.
 48. The aircraft system of claim 41 wherein the slot isconfigured to divert air sufficient to increase a critical Mach numberof the aircraft.
 49. The aircraft system of claim 41 wherein the slot isconfigured to divert air sufficient to increase a maximum cruise speedof the aircraft.
 50. An aircraft system, comprising: at least one winghaving a leading edge, an upper surface, and a lower surface, the uppersurface being shaped to include at least one transonic region duringcruise flight; and a trailing edge device carried by the at least onewing, the trailing edge device having an upper surface and a lowersurface, the upper surface of the trailing edge device being recessedaway from an aft-extended contour of the at least one wing upper surfacein a thickness direction along its entire length when in a neutral,undeflected position, at least one of the at least one wing and thetrailing edge device having a spanwise slot, the slot having anaft-facing exit opening at an offset between the upper surfaces of theat least one wing and the trailing edge device, the offset being in thethickness direction, the slot being configured to be open during cruiseflight to divert some of the air flowing along the lower surface of theat least one wing to flow over the upper surface of the trailing edgedevice, the slot being positioned to increase a Mach number at which theat least one wing undergoes transonic drag rise by about 0.03 comparedwith a wing having generally similar shape without the slot, the Machnumber corresponding to a component of flow travelling generally normalto the leading edge of the at least one wing.
 51. The aircraft system ofclaim 50, further comprising: a fuselage coupled to the at least onewing; a propulsion system depending from at least one of the at leastone wing and the fuselage; and landing gear depending from at least oneof the at least one wing and the fuselage.
 52. The aircraft system ofclaim 50 wherein the at least one wing is shaped to be efficient at atransonic condition.
 53. The aircraft system of claim 50 wherein the atleast one wing is at least approximately unswept.
 54. The aircraftsystem of claim 50 wherein the slot is configured to remain open at allflight conditions.
 55. The aircraft system of claim 50 wherein the atleast one wing includes at least one spar that is at least approximatelyunswept.
 56. The aircraft system of claim 50 wherein the slot extendsover less than an entire span of the at least one wing.
 57. The aircraftsystem of claim 50 wherein the at least one wing includes an aileron,and wherein the slot extends spanwise through a region of the at leastone wing containing the aileron.
 58. The aircraft system of claim 50wherein the slot is a first slot and wherein the trailing edge deviceincludes a forward portion and an aft portion, the forward portion andthe aft portion being movable as a unit relative to the at least onewing to form a second slot forward of the first slot and divertadditional air from the lower surface of the at least one wing to theupper surface of the trailing edge device.
 59. The aircraft system ofclaim 50 wherein the at least one wing overlaps the trailing edge deviceby a distance at least approximately equal to three percent of acombined chord length of the at least one wing and the trailing edgedevice.
 60. An aircraft system, comprising: at least one wing, the atleast one wing having an upper surface and a lower surface; an internalstructure including at least one spar; and an airfoil structureincluding a trailing edge device carried by the at least one wing, thetrailing edge device having an upper surface and a lower surface, theupper surface of the trailing edge device being recessed away from anaft-extended contour of the at least one wing upper surface in athickness direction along its entire length when in a neutral,undeflected, undeployed position, at least one of the at least one wingand the trailing edge device having a spanwise slot that allows airflowfrom the at least one wing to the trailing edge device, wherein duringcruising flight of the at least one wing, the airfoil structure divertssome of the air flowing along the lower surface of the at least one wingthrough the slot to flow over the upper surface of the trailing edgedevice.
 61. The aircraft system of claim 60 wherein the slot extendsover less than an entire span of the at least one wing.
 62. The aircraftsystem of claim 60 wherein the at least one wing includes an aileron,and wherein the slot extends spanwise through a region of the at leastone wing containing the aileron.
 63. A method for manufacturing anaircraft system, comprising coupling a trailing edge device to anaircraft wing, with the aircraft wing overlapping the trailing edgedevice by a distance at least approximately equal to three percent of acombined chord length of the aircraft wing and the trailing edge device,and with a spanwise slot positioned between at least part of theaircraft wing and at least part of the trailing edge device, the slotbeing configured to be open during cruise flight to divert some of theair flowing along a lower surface of the aircraft wing to flow over anupper surface of the trailing edge device, the upper surface of thetrailing edge device being recessed away from an aft-extended contour ofthe aircraft wing upper surface in a thickness direction along itsentire length when in a neutral, undeflected, undeployed position, theslot having an aft-facing exit opening at an offset between an uppersurface of the aircraft wing and the upper surface of the trailing edgedevice, the offset being in the thickness direction.
 64. The method ofclaim 63, further comprising: attaching the aircraft wing to a fuselage;connecting a propulsion system to at least one of the aircraft wing andthe fuselage; and coupling landing gear to at least one of the aircraftwing and the fuselage.
 65. The method of claim 63 wherein coupling atrailing edge device to an aircraft wing includes coupling the trailingedge device to an at least approximately unswept aircraft wing.
 66. Themethod of claim 63, further comprising configuring the slot to remainopen at all flight conditions.
 67. The method of claim 63, furthercomprising supporting the aircraft wing with at least one spar that isat least approximately unswept.
 68. The method of claim 63, furthercomprising positioning the slot to extend over less than an entire spanof the aircraft wing.
 69. The method of claim 63, further comprisingattaching an aileron to the aircraft wing and positioning the slot toextend spanwise through a region of the aircraft wing containing theaileron.
 70. A method for manufacturing an aircraft system, comprising:coupling a trailing edge device to an aircraft wing; and positioning aslot between at least part of the aircraft wing and at least part of thetrailing edge device to increase a Mach number at which the aircraftwing undergoes transonic drag rise by about 0.03 compared with anaircraft wing having a generally similar shape without the slot, theMach number corresponding to a component of flow travelling generallynormal to the leading edge of the aircraft wing, the slot beingconfigured to be open during cruise flight to divert some of the airflowing along a lower surface of the aircraft wing to flow over an uppersurface of the trailing edge device.
 71. The method of claim 70, furthercomprising: attaching the aircraft wing to a fuselage; connecting apropulsion system to at least one of the aircraft wing and the fuselage;and coupling landing gear to at least one of the aircraft wing and thefuselage.
 72. The method of claim 70 wherein coupling a trailing edgedevice to an aircraft wing includes coupling a trailing edge device toan at least approximately unswept wing.
 73. The method of claim 70,further comprising configuring the slot to remain open at all flightconditions.
 74. The method of claim 70, further comprising supportingthe aircraft wing with at least one spar that is at least approximatelyunswept.
 75. The method of claim 70, further comprising positioning theslot to extend over less than an entire span of the aircraft wing. 76.The method of claim 70, further comprising attaching ailerons to thewing and positioning the slot to extend spanwise through a region of thewing containing the ailerons.